Medication delivery apparatus including a medication metering system

ABSTRACT

A medication delivery apparatus ( 5 ) includes a reservoir for holding a liquid medication and a metering device ( 25 ) coupled to the reservoir for supplying a dose of the liquid medication to the reservoir. The metering device includes an upper chamber, a lower chamber coupled to the upper chamber, a piston selectively moveable within the upper chamber and the lower chamber and a valve providing selective fluid communication between the lower chamber and the reservoir in response to movement of the piston.

The present invention relates to medication delivery apparatus, such asnebulizers, and in particular, to a medication delivery apparatus havinga metering system for controlling the amount of medication that isprovided for delivery to a patient.

A number of devices are available for delivering a drug into the lungsof a patient. Once such device is a nebulizer, which is a device that isused for converting a liquid, such as a liquid medication, into anaerosol which is then inhaled by the patient, typically through amouthpiece. A number of different types of nebulizers exist, such as,without limitation, jet nebulizers (sometimes referred to as pneumaticnebulizers) and ultrasonic nebulizers. A typical jet nebulizer usescompressed air to generate the aerosol from the liquid. One type ofultrasonic nebulizer employs acoustic waves having an ultrasonicfrequency that are directed to a point on the surface of the liquid thatis to be converted into an aerosol. At the point on the surface of theliquid where these ultrasonic waves converge, they will producecapillary waves that oscillate at the frequency of the ultrasonic waves.If the amplitude of the waves is large enough, the peaks of thecapillary waves will break away from the liquid and be ejected from thesurface of the liquid in the form of droplets, thereby forming theaerosol. A device that is often used for generating ultrasonic waves inan ultrasonic nebulizer is a piezoelectric transducer (such as apiezoelectric crystal), which vibrates and generates ultrasonic waves inresponse to an applied electric field. In another type of ultrasonicnebulizer, the liquid that is to be converted into an aerosol is forcedthrough a mesh (thereby creating liquid droplets) by the vibration of apiezoelectric crystal acting upon a horn. In this type of ultrasonicnebulizer, typically referred to as a mesh nebulizer, the gauge of themesh determines the size of the droplets which are created to form theaerosol.

Conventional nebulizer systems provide a continuous aerosol/drug output,and thus the amount of drug inhaled is dependent upon the patient'sbreathing pattern. The duty cycle of the patient's breathing pattern istypically 40:60. This means that the patient spends 40 percent of asingle respiratory cycle in inspiration and 60 percent of the time inexpiration. Thus, 60 percent of the drug delivered from the nebulizerwill be wasted to the environment during expiration. In addition, thebreathing pattern of a single patient over the course of a treatmentwill vary.

In order to address these issues, more sophisticated nebulizer systems,referred to as adaptive nebulizer systems based on what is known asAdaptive Aerosol Delivery (AAD) technology, have been developed whichadapt the delivery of aerosol to the patient's breathing pattern,delivering medication only when the patient is inhaling through themouthpiece. Because adaptive nebulizer systems are able to deliver themedication very efficiently (nearly all of the medication supplied tothe nebulizer is actually delivered to the patient), it is importantthat the amount of medication supplied to the nebulizer be as precise aspossible so that the patient will receive the correct dose.

In one known method of controlling the volume of medication, a syringeis used to draw a precise amount of medication from a vial, and thedrawn medication is then transferred to a chamber in the nebulizer. Thismethod has a number of disadvantages. For example, patients with poordexterity, such as the elderly, may find it difficult to use a syringein this manner Also, the use of syringes presents the danger ofneedle-stick injuries, and sharps containers are required for disposal.Syringes also present an additional part that the patient must keeptrack of and carry with them when they leave their home.

United States Patent Application Publication Number 2003/0146300, ownedby the assignee of the present invention, describes a nebulizer thatincludes a nebulization device for nebulizing a medication and areservoir having a metering chamber arranged so as to feed themedication to the nebulization device and a second chamber arranged tohold and retain any of the medication that is in excess of the volumeheld in the metering chamber. While this approach is effective forcertain applications, there is room for improvement in the area ofnebulizers and methods for controlling the amount of medicationdelivered to the patient.

In one embodiment, a medication delivery apparatus is provided thatincludes a reservoir for holding a liquid medication and a meteringdevice coupled to the reservoir for supplying a dose of the liquidmedication to the reservoir. The metering device includes an upperchamber, a lower chamber coupled to the upper chamber, a piston, thepiston being selectively moveable within the upper chamber and the lowerchamber along a longitudinal axis of the upper chamber and the lowerchamber, and a valve, the valve providing selective fluid communicationbetween the lower chamber and the reservoir in response to movement ofthe piston. In one specific embodiment, the valve is a one-way valve(such as a duck-bill valve), wherein the valve is biased to be in anormally closed condition wherein the lower chamber is not in fluidcommunication with the reservoir and is structured to move to an opencondition wherein the lower chamber is in fluid communication with thereservoir in response to a force being applied to the valve as a resultof the piston moving toward the valve within the lower chamber.

In another particular embodiment, the lower chamber and the upperchamber are each cylindrical in shape, and the bore of the upper chamberis greater than the bore of the lower chamber. Also, the piston mayinclude a cylindrical bottom end having a seal element coupled thereto,the seal element being structured to engage the inner wall of the lowerchamber when the piston moves within the lower chamber.

In another particular embodiment, the piston is part of a cap that isstructured to be selectively coupled to the upper chamber. When the capis coupled to the upper chamber, the cap may be structured to berotatable relative to the upper chamber, wherein rotation of the capcauses the piston to move within the lower chamber. In this embodiment,the upper chamber may include a pin on the outer wall thereof, whereinthe cap includes an angled thread (such as a quarter turn thread),wherein the pin is structured to engage the thread when the cap iscoupled to the upper chamber.

In a different embodiment, when the cap is coupled to the upper chamber,the cap is structured to be movable relative to the upper chamberdownwardly and along the longitudinal axis of the upper chamber, whereinmovement of the cap causes the piston to move within the lower chamber.

The piston may include a central bore and a second valve in the centralbore, wherein the central bore is vented to atmosphere through a holeprovided in the cap.

The medication delivery apparatus may further include one or moreadditional caps that may be selectively coupled to the upper chamber,each of the one or more additional caps having an associated piston thatis different than the piston of the cap. The piston of the cap may havea first stroke, and one or more of the one or more additional caps eachmay have an associated piston having an associated stroke that isdifferent than the first stroke. The apparatus may further include aninsert structured to be received with the lower chamber, the lowerchamber having a first bore and the insert having a second bore that issmaller than the first bore, wherein one of the one or more additionalcaps has an associated piston that is sized and structured for use withthe insert.

The medication delivery apparatus may be a nebulizer, wherein thereservoir is part of an aerosol generation system, and wherein thereservoir holds the dose of the liquid medication to enable the dose ofthe liquid medication to be nebulized by the aerosol generation systemfor delivery to a patient.

In another embodiment, a method of providing a dose of a liquidmedication to a reservoir of a medication delivery apparatus is providedthat includes supplying an amount of the liquid medication to an upperchamber and a lower chamber of a metering device, the amount beinglarger than the dose, the lower chamber being coupled to the upperchamber, a first portion of the amount being held in the lower chamberand a second portion of the amount being held in the upper chamber,wherein the lower chamber is not in fluid communication with thereservoir under a static pressure of the first portion in the lowerchamber, and applying a force to the first portion in the lower chamberthrough the upper chamber, the force causing at least a part of thefirst portion to exit the lower chamber and be received in the reservoirof the medication delivery apparatus, the second portion beingmaintained within the metering device after application of the force.

These and other objects, features, and characteristics of the presentinvention, as well as the methods of operation and functions of therelated elements of structure and the combination of parts and economiesof manufacture, will become more apparent upon consideration of thefollowing description and the appended claims with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures. It is to be expressly understood, however, that thedrawings are for the purpose of illustration and description only andare not intended as a definition of the limits of the invention. As usedin the specification and in the claims, the singular form of “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise.

FIG. 1 is a side elevational view and

FIG. 2 is an isometric view of nebulizer device according to oneembodiment of the invention;

FIG. 3 is a schematic diagram of the nebulizer device of FIGS. 1 and 2which shows selected components thereof in a simplified or symbolicform;

FIG. 4 is a cross-sectional view and

FIG. 5 is a front elevational view of a metering device according to oneparticular embodiment;

FIGS. 6 and 7 are cross-sectional views of metering devices according toalternative embodiments of the present invention; and

FIGS. 8A, 8B and 8C are cross-sectional views of a metering deviceaccording to another particular embodiment.

Directional phrases used herein, such as, for example and withoutlimitation, top, bottom, left, right, upper, lower, front, back, andderivatives thereof, relate to the orientation of the elements shown inthe drawings and are not limiting upon the claims unless expresslyrecited therein.

As employed, herein, the statement that two or more parts or componentsare “coupled” together shall mean that the parts are joined or operatetogether either directly or through one or more intermediate parts orcomponents.

As employed herein, the statement that two or more parts or components“engage” one another shall mean that the parts exert a force against oneanother either directly or through one or more intermediate parts orcomponents.

As employed herein, the term “number” shall mean one or an integergreater than one (i.e., a plurality).

FIG. 1 is a side elevational view and FIG. 2 is an isometric view ofnebulizer device 5 according to one embodiment of the invention. FIG. 3is a schematic diagram of nebulizer device 5 which shows selectedcomponents thereof in a simplified or symbolic form. Nebulizer device 5functions as a drug delivery system for delivering a drug in the form ofaerosol 20 (FIG. 3) into the lungs of a patient. Nebulizer device 5includes main housing 10 which houses certain components (shown in FIG.3 and described below) of nebulizer device 5 and mouthpiece portion 15which is in the illustrated embodiment removeably attached to the mainhousing 10. Nebulizer device 5 also includes metering device 25,described in greater detail below, which is structured to control theamount of medication that is supplied to the internal components ofnebulizer 5 for conversion into aerosol 20 and ultimately delivery tothe patient. The mouthpiece portion 15 is structured to be received inthe mouth of the patient and includes a chamber which, when themouthpiece portion 15 is attached to the main housing 10, is structuredto receive the aerosol 20 that is generated by the components in themain housing 10 as described in more detail below. When the patientplaces his or her mouth on the end of the mouthpiece portion 15 andinhales, an air stream is created that carries the aerosol 20 into thelungs of the patient.

As seen in FIG. 3, nebulizer 5 includes mesh plate 30 (including aplurality of miniature holes therein), reservoir 35 for holding theliquid (drug) to be converted into aerosol 20, horn 40, andpiezoelectric transducer 45 operatively coupled to horn 40. Meteringdevice 25 is in fluid communication with reservoir 35, as indicated bythe arrow in FIG. 3, and, as described in greater detail herein, isstructured to deliver a controlled volume of liquid to reservoir 35 forconversion into aerosol 20. Nebulizer 5 also includes controller 50,which may be a microprocessor, microcontroller, or some other suitableelectronic control device or circuitry, and power supply 55, which maybe a rechargeable battery. Horn 40 is located close to the rear face ofmesh plate 30 and may be caused to vibrate by piezoelectric transducer45 under the control of controller 50, with the power to drivepiezoelectric transducer 45 being provided by power supply 55. Theliquid in reservoir 35 is in fluid contact with the rear face of themesh plate 30. When piezoelectric transducer 45 is caused to vibrate, itdrives horn 40 to vibrate in the region of mesh plate 30. As a result ofsuch vibration of horn 40, the liquid from reservoir 35 is forcedthrough the holes of mesh plate 30, thereby generating aerosol 20 (inthe form of a plume) that is injected into mouthpiece portion 15.

It should be understood that the mesh plate type aerosol generationsystem shown in FIG. 3 and just described is meant to be exemplary andis just one type of aerosol generation system that may be employed inconnection with the present invention. It is contemplated that otherstype of aerosol generation systems may be employed within the scope ofthe present invention. For example, and without limitation, an aerosolgeneration system that employs a piezeo element around the outside ofthe mesh and not a separate horn as in FIG. 3 may be employed. Asanother non-limiting example, a pneumatic type aerosol generation systemmay be employed.

FIG. 4 is a cross-sectional view and FIG. 5 is a front elevational viewof metering device 25 according to one particular embodiment. Meteringdevice 25 includes metering chamber 60 and cap 65. Metering chamber 60includes upper cylindrical chamber 70, lower cylindrical chamber 75, andport portion 80. As seen in FIGS. 3 to 5, the bore (i.e., innerdiameter) of upper cylindrical chamber 70 is larger that the bore (i.e.,inner diameter) of lower cylindrical chamber 75. In an exemplaryembodiment, metering chamber 60 is provided within main housing 10 ofnebulizer 5 and metering device 25 is provided as an integral part ofnebulizer 5 (see FIGS. 1 and 2). Alternatively, metering device 25 maybe detachable and selectively coupled to reservoir 35. In either case,port portion 80 is structured to be in fluid communication withreservoir 35 and includes internal one-way valve 85, which in theembodiment shown is a rubber duck-bill valve. Cap 65 includes internalpiston 90, outer wall 95 and sealing lip 100. Piston 90 is provided withsealing element 105, which in the illustrated embodiment is in the formof an O-ring, at cylindrical bottom end 110 of piston 90. In addition,pin 115 is provided on outer wall 120 of upper cylindrical chamber 70 ofmetering chamber 60, and angled quarter turn thread 125 is providedwithin outer wall 95 of cap 65, and is structured to receive pin 115.

In the particular embodiment where the one-way valve 85 is a rubberduck-bill valve, for the normal installation of the one-way valve 85, a10-15% axial compression of the flange is necessary with OD clearance topermit radial deformation. For proper function there should also be asmall clearance around the barrel (cylindrical portion) of the one-wayvalve 85. This ensures the valve normally requires a forward openingpressure to open the valve where 1 mbar is equivalent to 10 mmWG. Inaddition, to ensure the valve opening pressure is greater than theheight of the metering chamber 60, the flange of the one-way valve 85can be installed in an elliptical socket. If the flange is compressedalong the axis of the duck-bill, then the load will cause the valve 85to open. However, if the pressure is applied perpendicular to the axisof the duck-bill, then the load will stretch the duck bill and increasethe opening pressures.

In operation, a vial containing liquid medication is emptied intometering chamber 60 where it fills both lower cylindrical chamber 75 andoverflows into upper cylindrical chamber 70. The liquid medication isprevented from leaving the bottom of lower cylindrical chamber 75 byone-way valve 85. The volume of the liquid medication to be metered issubstantially determined by the volume of lower cylindrical chamber 75and the stroke of the piston 90. Depending on the viscosity of theliquid it may also fill the one-way valve 85. However the volume ofspace within the one-way valve 85 is small enough to not have a greateffect on the overall dose tolerance.

Cap 65 is then attached to metering chamber 60. In particular, piston 90is inserted into metering chamber 60 and pin 115 is received within andengages quarter turn thread 125.

Cap 65 is then moved in a one quarter turn. During this turn, cap 65 isguided and limited by the movement of quarter turn thread 125 over pin115. Also during this turn, seal element 105 engages with the inner wallsurface of lower cylindrical chamber 75 and provides a seal. Thisquarter turn of cap 65 drives bottom end 110 of piston 90 from the topto the bottom of lower cylindrical chamber 75. This movement deliversthe metered volume of the liquid medication from lower cylindricalchamber 75 through port portion 80 and valve 85 (pressure from piston 90causes valve 85 to open) to reservoir 35 of the mesh aerosol generationsystem of nebulizer 5. More specifically, valve 85 is biased to benormally in a closed condition (under the static pressure of the liquidin the lower cylindrical chamber 75) wherein lower cylindrical chamber75 is not in fluid communication with reservoir 35 and is structured tomove to an open condition wherein lower cylindrical chamber 75 is influid communication with reservoir 35 in response to a force beingapplied to the liquid in lower cylindrical chamber 75 and valve 85 as aresult of piston 90 moving toward valve 85 within lower cylindricalchamber 75. Any residual liquid will be contained in the lowercylindrical chamber 75 above bottom end 110 of piston 90 and the sealcreated by seal element 105.

Cap 65 may be removed by moving it a quarter turn in the oppositedirection. Piston 90 includes a central bore having a second one-wayvalve 135, which in the illustrated embodiment is a rubber duck-billvalve, which allows cap 65 to be removed from metering chamber 60without generating an air lock in metering chamber 60, and in particularlower cylindrical chamber 75. The area above valve 135 is vented toatmosphere via a small hole in cap 65.

As seen in FIG. 3, sealing lip 100 is structured to engage the interiorof the wall of upper cylindrical chamber 70 when cap 65 is fullylowered. This seal prevents the liquid remaining in metering chamber 60from leaking when metering device 25 is inverted.

As will be appreciated, the dose volume of the liquid medication that isexpelled from lower cylindrical chamber 75 and into reservoir 35 will besubstantially determined by the bore of lower cylindrical chamber 75 andthe stroke of piston 90. Thus, the dose volume may be controlled bycontrolling those features. FIG. 6 is a cross-sectional view of meteringdevice 25′ according to an alternative embodiment of the presentinvention having piston 90′ having a reduced stroke as compared topiston 90. This will result in a smaller dose volume. FIG. 7 is across-sectional view of metering device 25″ according to a furtheralternative embodiment of the present invention having lower cylindricalchamber 75″, formed by a generally cylindrically shaped insert providedin metering chamber 60, having a reduced bore as compared to lowercylindrical chamber 75. In addition, metering device 25″ includes piston90″ having bottom end 110″ having a reduce diameter as compared tobottom end 110. This also will result in a smaller dose volume.

According to an aspect of the invention, nebulizer device 5 may beprovided to the patient with multiple caps 65 each having a differentpiston 90, 90′, and 90″, and with one or more differently sized theinserts as shown in FIG. 7 so that the patient can selectively determinethe dose of liquid that is metered by selecting a particular cap 65and/or by using a particular insert. In one particular embodiment, thedimensions of the lower cylindrical chamber can be varied to meet thePRS of metered doses of 0.25 ml to 1.5 ml. The metering device asdescribed herein in the various embodiments is able to meter doses withan accuracy of +−/10%, which is required under certain regulatoryrequirements.

FIGS. 8A, 8B and 8C are cross-sectional views of metering device 150according to an alternative embodiment. Metering device 150 includesmetering chamber 155 and cap 160. Metering chamber 150 includes uppercylindrical chamber 165, lower cylindrical chamber 170, and port portion175. As seen in FIGS. 8A to 8C, the bore (i.e., inner diameter) of uppercylindrical chamber 165 is larger that the bore (i.e., inner diameter)of lower cylindrical chamber 170. In an exemplary embodiment, meteringchamber 155 is provided within main housing 10 of nebulizer 5 andmetering device 150 is provided as an integral part of nebulizer 5.Alternatively, metering device 150 may be detachable and selectivelycoupled to reservoir 35. In either case, port portion 175 is structuredto be in fluid communication with reservoir 35 and includes internalone-way valve 180, which in the embodiment shown is a rubber duck-billvalve. Cap 160 includes internal piston 185, outer wall 190 and sealinglip 195. Piston 185 is provided with sealing element 200, which in theillustrated embodiment is in the form of an O-ring, at cylindricalbottom end 205 of piston 185.

In operation, a vial containing liquid medication is emptied intometering chamber 155 where it fills both lower cylindrical chamber 170and overflows into upper cylindrical chamber 165. The liquid medicationis prevented from leaving the bottom of lower cylindrical chamber 170 byone-way valve 180. The volume of the liquid medication to be metered issubstantially determined by the volume of lower cylindrical chamber 170and the stroke of piston 185. Depending on the viscosity of the liquidit may also fill one-way valve 180. However the volume of space withinthe one-way valve 180 is small enough to not have a great effect on theoverall dose tolerance. Cap 160 is then coupled to metering chamber 155by inserting piston 185 into metering chamber 155 and pushing cap 160downward. During this downward movement, seal element 200 engages withthe inner wall surface of lower cylindrical chamber 170 and provides aseal and bottom end 205 of piston 185 is driven from the top to thebottom of lower cylindrical chamber 170. This movement delivers themetered volume of the liquid medication from lower cylindrical chamber170 through port portion 175 and valve 180 (pressure from piston 185causes valve 180 to open) to reservoir 35 of the mesh aerosol generationsystem of nebulizer 5 as described in more detail elsewhere herein. Anyresidual liquid will be contained in the lower cylindrical chamber 170above bottom end 205 of piston 185 and the seal created by seal element200.

Cap 160 may be removed by pulling upwardly on it. Piston 185 includes acentral bore 215 having a second one-way valve 210, which in theillustrated embodiment is a rubber duck-bill valve, which allows cap 160to be removed from metering chamber 155 without generating an air lockin metering chamber 155, and in particular lower cylindrical chamber170. The area above valve 210 is vented to atmosphere via a small holein cap 160. In addition, sealing lip 195 is structured to engage theinterior of the wall of upper cylindrical chamber 165 when cap 160 isfully lowered. This seal prevents the liquid remaining in meteringchamber 155 from leaking when metering device 150 is inverted.

Furthermore, the metering device as described herein in the variousembodiments may also be designed so that it can only be used in specificnebulizers by keying the external shape of the metering chamber 60 tothe device in which it is to be used.

While the present invention has been described in connection with anebulizer, it should be understood that that is not meant to be limitingand that the present invention may be employed in connection with othertypes of medication delivery devices.

Although the invention has been described in detail for the purpose ofillustration based on what is currently considered to be the mostpractical and preferred embodiments, it is to be understood that suchdetail is solely for that purpose and that the invention is not limitedto the disclosed embodiments, but, on the contrary, is intended to covermodifications and equivalent arrangements that are within the spirit andscope of the appended claims. For example, it is to be understood thatthe present invention contemplates that, to the extent possible, one ormore features of any embodiment can be combined with one or morefeatures of any other embodiment.

1. A medication delivery apparatus (5), comprising: a reservoir (35) forholding a liquid medication; and a metering device (25, 150) coupled tothe reservoir for supplying a dose of the liquid medication to thereservoir, the metering device including: an upper chamber (70, 165); alower chamber (75, 170) coupled to the upper chamber; a piston (90,185), the piston being selectively moveable within the upper chamber andthe lower chamber along a longitudinal axis of the upper chamber and thelower chamber; and a valve (85, 180), the valve providing selectivefluid communication between the lower chamber and the reservoir inresponse to movement of the piston.
 2. The medication delivery apparatusaccording to claim 1, wherein the valve is a one-way valve, wherein thevalve is biased to be in a normally closed condition wherein the lowerchamber is not in fluid communication with the reservoir and isstructured to move to an open condition wherein the lower chamber is influid communication with the reservoir in response to a force beingapplied to the valve as a result of the piston moving toward the valvewithin the lower chamber.
 3. The medication delivery apparatus accordingto claim 2, wherein the valve is a duck-bill valve.
 4. The medicationdelivery apparatus according to claim 1, wherein the lower chamber andthe upper chamber are each cylindrical in shape, and wherein a bore ofthe upper chamber is greater than a bore of the lower chamber.
 5. Themedication delivery apparatus according to claim 4, wherein the pistonincludes a cylindrical bottom end (110, 205) having a seal element (105,200) coupled thereto, the seal element being structured to engage aninner wall of the lower chamber when the piston moves within the lowerchamber.
 6. The medication delivery apparatus according to claim 1,wherein the piston is part of a cap (65, 160) that is structured to beselectively coupled to the upper chamber.
 7. The medication deliveryapparatus according to claim 6, wherein when the cap is coupled to theupper chamber, the cap is structured to be rotatable relative to theupper chamber, and wherein rotation of the cap causes the piston to movewithin the lower chamber.
 8. The medication delivery apparatus accordingto claim 7, wherein the upper chamber includes a pin (115) on an outerwall thereof, wherein the cap includes an angled thread (125), whereinthe pin is structured to engage the thread when the cap is coupled tothe upper chamber.
 9. The medication delivery apparatus according toclaim 8, wherein the thread is a quarter turn thread.
 10. The medicationdelivery apparatus according to claim 6, wherein when the cap is coupledto the upper chamber, the cap is structured to be movable relative tothe upper chamber along the longitudinal axis of the upper chamber, andwherein movement of the cap causes the piston to move within the lowerchamber.
 11. The medication delivery apparatus according to claim 6,wherein the piston includes a central bore (130, 215) and a second valve(135, 210) in the central bore, and wherein the central bore is ventedto atmosphere through a hole provided in the cap.
 12. The medicationdelivery apparatus according to claim 6, wherein the medication deliveryapparatus further comprises one or more additional caps that may beselectively coupled to the upper chamber, each of the one or moreadditional caps having an associated piston that is different than thepiston of the cap.
 13. The medication delivery apparatus according toclaim 12, wherein the piston of the cap has a first stroke, and whereinone or more of the one or more additional caps each having an associatedpiston having an associated stroke that is different than the firststroke.
 14. The medication delivery apparatus according to claim 12,further comprising an insert structured to be received with the lowerchamber, the lower chamber having a first bore and the insert having asecond bore that is smaller than the first bore, wherein one of the oneor more additional caps has an associated piston that is sized andstructured for use with the insert.
 15. The medication deliveryapparatus according to claim 1, wherein the medication deliveryapparatus is a nebulizer (5), wherein the reservoir is part of anaerosol generation system, and wherein the reservoir holds the dose ofthe liquid medication to enable the dose of the liquid medication to benebulized by the aerosol generation system for delivery to a patient.16. A method of providing a dose of a liquid medication to a reservoir(35) of a medication delivery apparatus (5), comprising: supplying anamount of the liquid medication to an upper chamber (70, 165) and alower chamber (75, 170) of a metering device (25, 150), the amount beinglarger than the dose, the lower chamber being coupled to the upperchamber, a first portion of the amount being held in the lower chamberand a second portion of the amount being held in the upper chamber,wherein the lower chamber is not in fluid communication with thereservoir under a static pressure of the first portion in the lowerchamber; and applying a force to the first portion in the lower chamberthrough the upper chamber, the force causing at least a part of thefirst portion to exit the lower chamber and be received in the reservoirof the medication delivery apparatus, the second portion beingmaintained within the metering device after application of the force.17. The method according to claim 16, wherein the applying the forceincludes applying the force by moving a piston (90, 185) within theupper chamber and the lower chamber.
 18. The method according to claim17, wherein the piston engages an inner wall of the lower chamber andprovides a seal when the piston moves within the lower chamber.
 19. Themethod according to claim 17, wherein the piston is part of a cap (65,160), wherein the applying a force further comprises coupling the cap tothe upper chamber and rotating the cap relative to the upper chamber,and wherein rotation of the cap causes the piston to move within thelower chamber.
 20. The method according to claim 19, wherein the upperchamber includes a pin (115) on an outer wall thereof, wherein the capincludes an angled thread (125), wherein the coupling comprises causingthe pin to engage the thread, and wherein the thread moves relative tothe pin when the cap is rotated relative to the upper chamber.
 21. Themethod according to claim 18, wherein the piston is part of a cap,wherein the applying a force further comprises coupling the cap to theupper chamber and moving the cap relative to the upper chamber along alongitudinal axis of the upper chamber.
 22. The method according toclaim 16, wherein the metering device includes a valve (85, 180)providing selective fluid communication between the lower chamber andthe reservoir, wherein the valve is biased in a normally closedcondition under the static pressure wherein the lower chamber is not influid communication with the reservoir and wherein the applying a forcecauses the valve to move to an open condition wherein the lower chamberis in fluid communication with the reservoir.
 23. The method accordingto claim 19, wherein rotation of the cap causes the piston to movewithin the lower chamber in a first direction, wherein the pistonincludes a central bore (130, 215), and wherein the method furtherincludes venting the central bore to atmosphere as the piston is movedin a second direction opposite the first direction.
 24. The methodaccording to claim 21, wherein the cap is one of a plurality of providedcaps, wherein each one of the plurality of provided caps other than thecap has an associated piston having that is different than the piston ofthe cap, and wherein the method further comprises selecting the cap fromamong the number of provided caps.
 25. The method according to claim 24,wherein the piston of the cap has a first stroke, and wherein each oneor more of the plurality of provided caps other than the cap has anassociated piston having an associated stroke that is different than thefirst stroke.
 26. The method according to claim 24, further comprisingcreating the lower chamber by inserting an insert into a meteringchamber of the metering device, the metering chamber including the upperchamber, wherein the piston of the cap is sized and structured for usewith the insert.